Seismicity of the Shabla-Kaliakra-Balchik region over the period 1986-2014

Summary We study spatial and temporal properties of the seismic activity in the Shabla-Kavarna-Balchik region over the period 1986–2014. This region is located in the NE part of Bulgaria (longitude range between 27.75E and 30.0E, and latitude range between 43.0N and 44.3N). The seismic activity there is related to a multitude of onshore and offshore faults. We use data from the Bulgarian National Seismic Network to identify 204 earthquakes in the region for the considered period. We find that the seismic activity rate increases abruptly after the August 5th 2009 Md=4.7 offshore earthquake. We identify the most active faults in the region for the considered period: (1) the Kaliakra fault; (2) the Batovo fault; (3) the Shabla fault; (4) the Razelm fault, as well as several near-coastal NNE-SSW faults where the aftershocks of the strong quake of August 2009 concentrated. The spatiotemporal behviour of the earthquake activity in the region suggests possible interaction between adjacent or intersecting regional faults.